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The REAL John Linsley Hood Headphone Amplifier
The REAL John Linsley Hood Headphone Amplifier
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Old 11th April 2018, 02:54 PM   #31
anti is offline anti  Slovakia
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Warning: Headphones "stole" the amp thread!
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Old 11th April 2018, 04:11 PM   #32
DJDestiny is offline DJDestiny  Singapore
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Quote:
Originally Posted by EUVL View Post
HD662 or 662 EVO ?
Superlux HD662 EVO im Test bei kopfhoerer.de
Superlux HD662 im Test bei kopfhoerer.de
(Just use Google translate).

And the diy heaven mods work as claimed.
I shall gladly pay the 30 (including delivery) any time again, if I happen to destroy this one in amp testing.




Patrick
662 non evo. That one is not bad actually, the ones that aren't all that great is the 681 but eh... it was only 20 bucks.
I have very cheap iems I use for amp testing... would have been handy when I first started and accidentally bridged the power and output pins on a opamp!
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Old 11th April 2018, 04:19 PM   #33
Nisbeth is offline Nisbeth  Denmark
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The REAL John Linsley Hood Headphone Amplifier
FWIW the original page of the headphone amplifier designs (and all the other JLH information from Geoff Moss' site) is still hosted by Rod Elliot.

HP amps

Main page

/U.
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Old 11th April 2018, 05:18 PM   #34
EUVL is offline EUVL  Europe
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Thanks for the links.


Patrick
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Old 16th April 2018, 10:29 AM   #35
EUVL is offline EUVL  Europe
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As promised the article on the Linsley Hood 1985 Headphone Amplifier.
The Bill of Material is based on the 4 prototypes we built.
It may be subjected to further changes after Beta testing.

As mentioned, we shall publish Gerber files of a public version of the PCB after Beta testing as a tribute to the late Mr. Linsley Hood.
You can then order PCBs yourself.


In the meantime happy reading,
Patrick

.
Attached Files
File Type: pdf JLH 1985 HPA Description V1a.pdf (816.4 KB, 237 views)
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Old 16th April 2018, 12:01 PM   #36
Bigun is offline Bigun  Canada
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The REAL John Linsley Hood Headphone Amplifier
I apologize if I missed something, but your thread title emphasises that it is the real JLH (what attracted me to it) but you are advertising a new circuit that is not the real JLH but rather is your own derivative. At the same time, your give the feeling of this being a commercial venture with free advertising for your company in a DIY forum using JHL name for marketing which doesn't feel nice ? At least the eBay sellers are using an actual JLH circuit.

I have made threads where I've started with a famous design and then modified it. I always ensure the thread title says something like "new design inspired by JLH", if you get my drift.
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Last edited by Bigun; 16th April 2018 at 12:29 PM.
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Old 16th April 2018, 01:11 PM   #37
EUVL is offline EUVL  Europe
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I did mention that the PCB is suitable for both the original and the modified version.
And we offer the Gerbers for free.
So where is the commercial interest ?

We do not make money with audio.
We have other means to make a comfortable living.
And certainly we do not need any advertising.


Cheers,
Patrick
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Old 16th April 2018, 03:07 PM   #38
Bigun is offline Bigun  Canada
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The REAL John Linsley Hood Headphone Amplifier
All I can say it is the feeling your writing gave me. Perhaps just a language thing but it does seem the focus is on the derivative circuit rather than the original JLH design. And when you write 'we' in your thread I assume it is in reference to your 'xen-audio' (where it is posted that you charge 100 Euro's an hour - I don't care if you make a profit or not, you are not a Registered Charity) - it does not feel like the same thing as somebody saying 'I built this' circuit for my hobby.

I applaud you for providing Gerber files. I also provide free Gerbers for my projects and I have been known to help people from time to time with their hobby work which is what I believe is the spirit of this forum just as I have received help.
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Last edited by Bigun; 16th April 2018 at 03:11 PM.
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Old 16th April 2018, 03:40 PM   #39
EUVL is offline EUVL  Europe
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We would like to add a few more sentences to explain our motivations for changing the original circuit.
(Yes, we have a team who work together on these builds.)

In the original article, it was said that
"Fortunately the headphone amp has a much easier job to do, in that neither the output power requirements nor the load characteristics are so severe, since headphones typically have a load impedance of 100-2000 ohm, and only require 1-2Vrms, for normal output."

This might well be true some 30 years ago.
Today, a lot of the modern-day headphones are of low impedance, typically 30~50 ohm, some ven 16 ohm.
For example, the Pass HPA-1 was tested in the Stereophile review for distortion at 1Vrms into 30 ohm.
Pass Labs HPA-1 headphone amplifier Measurements | Stereophile.com
If one were to stick to the original JLH 1985 circuit, one would find distortion level at the -65dB region.
That just does not do justice to the JLH topology itself.

We typically test headphone amplifiers with loads of 30 ohm, 65 ohm, 100 ohm and 600 ohm.
And they should sound good over the entire range.
We know beforehand that the original JLH would not be up to the task at 30 ohm, because it was not designed for that.
On top of that, if we had stuck to the original circuit, we would hav ebeen accused of including electrolytic caps in the signal path.

Therefore, as we already explained in the article, we took the liberty of reporting the few changes we made to make it more relevant today.
Just as we recommended using readily available components in the 21 century.
This is by no means meant to be a disregard for Mr. Linsley Hood.
As we have mentioned more than once, those interested should build both versions and compare them for themselves.

Whether our publication here is appreciated or not makes no difference to us.
We have a clear conscience.

This will in fact be the second last headphone amplifier circuit we shall build and publish, for the foreseeable future.
We have one more legendary circuit that was actually finsihed before the JLH, but still awaits auditioning.
In that particular case, we are fortunate enough to be able to contact the original design for review and approval of the article.
As those who follow our projects would know, these classic designs were built primarily as benchmarks against which we compare our own.

That's all on this particular topic.


Cheers,
Patrick
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Old 16th April 2018, 06:28 PM   #40
EUVL is offline EUVL  Europe
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A reminder for those who wish to read the original JLH article.
Please refer to post #12 and #33.

There is also a Spice file of the above in post #4, so that you can check the performance in simulation under different opperating conditions.


Patrick
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